I'm looking for an off-the-shelf 4-wheel electric-powered platform for an outdoor robot with the following characteristics:

About the size of a standard push lawnmowerWheels around 8 to 10 inches in diameter for good ground clearance4 wheels equal in sizeSpeed around 3 to 5 mphCosts less than $500

I suspect that no such thing is available on the market, but I thought I'd ask. The closest thing I've found is a kids Power Wheels type car, but these require so much modification, it's probably easier to build one from scratch. Other than that there are the R/C trucks, but these are either too small (the 1:8 scale category) or cost $1K-$2K and up (1:6 to 1:4 scale). There is the Superdroids All Terrain Platform, but it's too small and too expensive. There is the Machine Labs line of platforms but they are in the $4K price range.

Why such a big robot? It's all-terrain. I've found that for all-terrain you need big wheels, a lot of ground clearance, and powerful motors. Big wheels means at least 8 inches diam. The Lynxmotion is too small.

Wheelchair motors are fine if you can get them for cheap. However, I think Power Wheels motors will be sufficient, and they are very cheap even brand new. That is my current plan, but I just wanted to check if anyone had come across something off-the-shelf.

4by4, you want a difficult size for your robot, it's a size that's not very common...I see two choices:easy: go for something smaller. Then the best choice is to go for an RC offroad truck (buy a quality one!!)hard: custom build your own big robot. But building your own suspension system etc, is NOT easy.

If there are no very important reasons you want to go so big, I recommend the easy choice.

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Their RT-4 model is exactly what I want. Only problem is it costs >5,000 euros! The high cost for this sort of thing is due to the fact that they have to amortize the engineering cost over a small numbers of unit sales. Same goes for the Machine Labs products.